package com.lagou.sqlSession;

import com.lagou.config.BoundSql;
import com.lagou.pojo.Configuration;
import com.lagou.pojo.MappedStatement;
import com.lagou.utils.GenericTokenParser;
import com.lagou.utils.ParameterMapping;
import com.lagou.utils.ParameterMappingTokenHandler;

import java.beans.PropertyDescriptor;
import java.lang.reflect.Field;
import java.lang.reflect.Method;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.ResultSetMetaData;
import java.util.ArrayList;
import java.util.List;

/**
 * description SimpleExecutor
 * author wy
 * date 2021-04-07 20:36
 **/
public class SimpleExecutor implements Executor
{
    public PreparedStatement prepare(Configuration configuration, MappedStatement mappedStatement, Object... params) throws Exception
    {
        //1 注册驱动，获取链接
        Connection connection = configuration.getDataSource().getConnection();

        //2 获取sql,转换sql
        String sql = mappedStatement.getSql();
        BoundSql boundSql = getBoundSql(sql);

        //3 获取预处理对象
        PreparedStatement preparedStatement = connection.prepareStatement(boundSql.getSqlText());

        //4 设置参数
        String paramterType = mappedStatement.getParamterType();
        Class<?> parameterTypeClass = getClassType(paramterType);

        List<ParameterMapping> parameterMappingList = boundSql.getParameterMappingList();
        for (int i = 0; i < parameterMappingList.size(); i++)
        {
            ParameterMapping parameterMapping = parameterMappingList.get(i);
            String content = parameterMapping.getContent();

            Field declaredField = parameterTypeClass.getDeclaredField(content);
            //设置暴力访问
            declaredField.setAccessible(true);
            Object o = declaredField.get(params[0]);

            preparedStatement.setObject(i + 1, o);

        }
        return preparedStatement;
    }

    @Override
    public <E> List<E> query(Configuration configuration, MappedStatement mappedStatement, Object... params) throws Exception
    {
        PreparedStatement preparedStatement = this.prepare(configuration, mappedStatement, params);
        //5 执行
        ResultSet resultSet = preparedStatement.executeQuery();

        String resultType = mappedStatement.getResultType();
        Class<?> resultTypeClass = getClassType(resultType);

        ArrayList<Object> objects = new ArrayList<>();

        //6 封装结果集
        while (resultSet.next())
        {
            Object o = resultTypeClass.newInstance();
            ResultSetMetaData metaData = resultSet.getMetaData();
            for (int i = 1; i <= metaData.getColumnCount(); i++)
            {
                //字段名
                String columnName = metaData.getColumnName(i);
                //字段的值
                Object value = resultSet.getObject(columnName);

                PropertyDescriptor propertyDescriptor = new PropertyDescriptor(columnName, resultTypeClass);
                Method writeMethod = propertyDescriptor.getWriteMethod();
                writeMethod.invoke(o, value);
            }
            objects.add(o);
        }

        return (List<E>) objects;
    }

    @Override
    public int insert(Configuration configuration, MappedStatement mappedStatement, Object... params) throws Exception
    {
        PreparedStatement preparedStatement = this.prepare(configuration, mappedStatement, params);
        preparedStatement.execute();
        return preparedStatement.getUpdateCount();
    }

    @Override
    public int update(Configuration configuration, MappedStatement mappedStatement, Object... params) throws Exception
    {
        PreparedStatement preparedStatement = this.prepare(configuration, mappedStatement, params);
        preparedStatement.execute();
        return preparedStatement.getUpdateCount();
    }

    @Override
    public int delete(Configuration configuration, MappedStatement mappedStatement, Object... params) throws Exception
    {
        PreparedStatement preparedStatement = this.prepare(configuration, mappedStatement, params);
        preparedStatement.execute();
        return preparedStatement.getUpdateCount();
    }


    private Class<?> getClassType(String paramterType) throws ClassNotFoundException
    {
        if (paramterType != null)
        {
            Class<?> aClass = Class.forName(paramterType);
            return aClass;
        }
        return null;
    }

    /**
     * 完成对#{}的解析工作，1.将#{}替换成？，2.获取#{}里面的内容
     *
     * @param sql
     * @return
     */
    private BoundSql getBoundSql(String sql)
    {
        ParameterMappingTokenHandler parameterMappingTokenHandler = new ParameterMappingTokenHandler();
        GenericTokenParser tokenParser = new GenericTokenParser("#{", "}", parameterMappingTokenHandler);
        //解析出来的sql
        String text = tokenParser.parse(sql);
        //解析出来的参数名称
        List<ParameterMapping> parameterMappings = parameterMappingTokenHandler.getParameterMappings();

        BoundSql boundSql = new BoundSql(text, parameterMappings);
        return boundSql;
    }

}
